New Member with a Question About my 2006 Sierra

[archaeon]

Howdy,
Writing this from St.Petersburg Florida, glad to find this forum. I didn't see a forum for repair questions, so I'll ask here for the time being.
I need to get another catalytic converter. I'm trying to keep cost down, but get a decent one that has the correct pressure for a 2006 GMC Sierra 1500 standard work truck. I need advice on what coil packs to get as well.
Thank for any help offered. This is my first GMC truck and I love it.
Nic Weathersbee

[Mike GMC]

For the cat, I'd just recommend a new stock replacement. Why do you think you need coils? Do you have misfire issues? Are you trying to make upgrades?

[2018GMC]

Rockauto or summitracing will have standard or high flow replacement converters. Most likely a lot cheaper than your local auto parts store.

[archaeon]

Thanks for the replies. Went to a muffler shop, guy says cat is bad, rattling and expanded because truck is running rich. He said if i put a cat on without replacing coils, it will ruin the new cat, same as the old one.

My mechanic says only put on factory cat. They are expensive though. I was looking on ebay and found magnaflows for about 500. Just trying to find the least expensive route to go that wont hurt the engine. Mechanic says aftermarket cats will hurt the motor. Its not backfiring, just rattling like hell from the expanded cat.

[archaeon]

Will check out rock auto and summit racing, thanks.

[diyer2]

Why would coils ruin a cat? IMO coils will cause a misfire when bad.

[archaeon]

He said if the coils haven't been changed since 06, would be a good idea to replace before adding the new cat. He said its running rich, thsts what destroyed the cat. Im no expert, lol, just reporting what the guy said.

[kstruckcountry]

Running rich and coil packs are two different issues. Is there a check engine light for either? Might want to find a better mechanic.

 

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[archaeon]

He said if the coils haven't been changed since 06, would be a good idea to replace before adding the new cat. He said its running rich, thsts what destroyed the cat. Im no expert, lol, just reporting what the guy said.

[e_schott]

If you have a bad coil, the misfire will often lead to a rich fuel mixture and or raw fuel getting into the cat. When raw fuel gets into the cat, it will burn out the cat and ruin it. So the mechanic is somewhat correct in the statement he has made. However, a rich fuel mixture can be caused by more than a bad coil, and that is something that you should have diagnosed and corrected before installing a new cat. I will say in my experience, coils on these trucks last pretty long, if you are not having any misfire issues I would not be looking at them, but it could possibly be the cause of a rich fuel mixture, as I said though it really needs to be diagnosed by someone who is competent at diagnosing engine performance issues.

 

As far as the cat goes, I have installed many aftermarket converters on these trucks and never had one comeback or customer complaint from it. It's over 10 years old...don't break the bank on the cat. A replacement cat assembly with the y pipe in one assembly can easily be had for less than $300, or if you are just replacing one side you can easily have that for $150-$175 if I recall the pricing of these things correctly. Hopefully this helps a little and if you have any other questions let me know.

[Mike GMC]

I would agree that the coils can last a very long time. My 2000 has over 215k miles and still has all 8 stock coils. The rich issue is more likely an injector or O2 sensor. If you don't have misfires, I'd look elsewhere for the issue.

[archaeon]

Thank you guys very much for the great replies. I'll diagnose the rich running issue, then find a decent cat that was recommended.

[e_schott]

Thank you guys very much for the great replies. I'll diagnose the rich running issue, then find a decent cat that was recommended.

Do you have a basic scanner that can provide live data? This will greatly help you in diagnosing this issue because you will need to monitor O2 voltages and fuel trims to rule out the culprit of the rich condition. Or if you pull codes and there are several misfire codes in addition to a rich code you may end up having an issue with the coils. As I said before, coils do last on these trucks pretty long but every now and then I do replace them in the shop at various miles, although much less often than ford and dodge trucks.

[muddkatt]

Florida doesn't require smog testing, just gut the cat and reinstall it. My 01 has been gutted for about 160,000 miles now. I also suggest you find a different mechanic because there is no need to change 8 working coils just because of age. The 01 has all 8 original coils and plug wires and has 315K miles on it.

[archaeon]

I should have mentioned that the truck has 223,000 miles. Also there are two mechanics, the muffler guy who said replace the coils, and my mechanic who has not diagnosed the need to replace the coils yet. The mechanic I have is a Vietnamese mechanic who is very very very good from what I'm told. One of the issues is he can't connect to my computer. I researched this a little bit and found that the fuse that controls the lighter plugs also controls the computer. First I'm going to have him check the fuses to see if that's the issue because my lighter sockets are not working. They just stopped working because one of them has something jammed in it. I was using the left one and then it stopped working. So I think that's the issue why he can connect to the computer. That's the first issue I'm going to address. Once he can talk to the computer I will address the richness issue and then go from there. I only dropped my truck off with my new mechanic briefly so he didn't have time to really look into everything. He just fixed the things that needed to be fixed right away and I'm going to take it back.